Method for manufacturing metal film having high purity

ABSTRACT

Methods for manufacturing metal films, and more particularly, to a method for manufacturing a cobalt film, a rhodium film or an iridium film having high purity via a CVD method without using reaction gas at low deposition temperature. Metal films having high purity may be deposited without impurities such as carbon, hydrogen or oxygen by using disproportionate reaction at low temperature because side-products such as L and MX 3 , which are neutral materials having high vapor pressure, are easily removed from a reactor by vacuum without remaining in the films. Additionally, almost no particles are generated because reaction gas is not used.

BACKGROUND

[0001] 1. Technical Field

[0002] Methods for manufacturing metal films are disclosed, and more particularly, methods for manufacturing a cobalt film, a rhodium film or an iridium film are disclosed wherein the films have a high purity via a Chemical Vapor Deposition (hereinafter, referred to as ‘CVD’) process without using reaction gas at a low deposition temperature.

[0003] 2. Description of the Related Art

[0004] Generally, when semiconductor devices are manufactured, various processes are employed to form thin films. Particularly, a CVD process which provides improved step coverage and deposition rate of films is used to obtain uniform thin films.

[0005] In the CVD process, thin films or epitaxial layers are formed on semiconductor substrates from decomposed gaseous compounds by chemical reaction. Here, the formation process of the thin films is carried out using reaction gas which is injected into a reaction chamber from outside, not using materials on the semiconductor substrates.

[0006] The conventional CVD methods uses source in gas state to grow thin films. However, in case of high dielectric material or wiring materials, the thin films are deposited using metal precursor in solid source or metal precursor in liquid source due to difficulties in vaporizing those materials.

[0007] The above process is performed in a device comprising a source supply, a vaporizer and a reactor. The sources from the source supply are injected in the vaporizer. The temperature of the vaporizer is maintained at temperature higher than vaporization temperatures of the sources and lower than reaction temperatures or deposition temperatures of the sources. Therefore, the injected metal precursor in solid or liquid sources are vaporized instantly in the vaporizer maintained at high temperature. Then, the vaporized source is injected into the reactor by carrier gas and reacts with reaction gas to form a desired thin film on a semiconductor substrate.

[0008] In the conventional CVD method for manufacturing metal films such as iridium film or rhodium film, precursors such as MX or MX₃ where M is cobalt, iridum or rhodium having oxidation number of metal of +1 or +3 is used as precursors, and wherein oxygen or hydrogen is used as reaction gas, and wherein X is anion ligand.

[0009] According to the reaction mechanism, when metal films are deposited, oxygen reacts with the metal precursor MX or MX₃ to reduce or oxidize metal. In addition, oxygen reacts with anion ligand X to make the side-product. Here, neutral side-product made from oxidation-reduction reaction may be removed using a vacuum. However, anion or cation side-products remain in the films because they difficult to remove.

[0010] Decomposition reaction of oxygen and ligand is complicated and fast. As a result, impurities such as carbon, hydrogen and oxygen remain in metal films. Those impurities diffuse into other films during the subsequent thermal process or deposition process, thereby deteriorating characteristics of film.

[0011] In addition, in the conventional CVD method using oxygen, the oxygen reacts with metal precursor MX or MX₃ under gaseous atmosphere to cause decomposition reaction, by which lump of inactive materials such as carbonate or oxide are formed on the films to generate particles.

[0012] Accordingly, in order to solve the problem in the CVD method using the oxygen, hydrogen which is a reduction gas may be used instead of oxygen. However, the deposition temperature should be greater than 700° C. to activate hydrogen, which causes the metal precursor MX or MX₃ to self-decompose to form carbonate. As a result, impurities still remain in the films.

[0013] When metal films are used as upper electrodes on oxide films such as Ta₂O₅ film, BST film, PZT film or SBT film, hydrogen used under high temperature environment reduces the oxide film. As a result, desired electric characteristics cannot be obtained.

SUMMARY OF THE DISCLOSURE

[0014] Accordingly, methods for manufacturing a cobalt film, rhodium film or iridium film are disclosed wherein the films have a high purity via a CVD method at a low deposition temperature without using reaction gas such as oxygen or hydrogen by using a disproportionate reaction of a metal precursor wherein oxidation number of the metal is +1.

[0015] A disclosed method for manufacturing a metal film comprises:

[0016] (a) vaporizing a metal precursor M(L)X, where M is a metal, L is a neutral ligand and X is an anion ligand, wherein the metal M has an oxidation number of +1;

[0017] (b) adsorbing the vaporized metal precursor on a semiconductor substrate heated to a temperature ranging from 100 to 900° C. to deposit metal layer on the substrate; and

[0018] (c) pumping out the side-product generated during the step (b).

[0019] First, the metal precursor having a structure formula M(L)X wherein the metal M has an oxidation number of +1 is explained. Here, the M, which is metal, is preferably selected from the group consisting of cobalt, rhodium and iridium, the L is neutral ligand, and X is anion ligand.

[0020] Pure solid state of M(L)X or M(L)X solution having a molarity ranging from 0.05 to 10M is used for metal precursor. Here, solvent used in the M(L)X solution is selected from the group consisting of C₁-C₂₀ alkane, C₂-C₂₀ alkene, C₂-C₂₀ alkyne, C₁-C₂₀ alcohol, C₂-C₂₀ ether, C₂-C₂₀ carboxylic acid, C₃-C₂₀ ester, C₃-C₂₀ β-diketone, C₁-C₂₀ amine, C₆-C₂₀ arene, C₄-C₂₀ cyclic alkane, C₃-C₂₀ cyclic ether, C₁-C₂₀ alkane substituted with halogen, C₂-C₂₀ alkene substituted with halogen, C₂-C₂₀ alkyne substituted with halogen, C₁-C₂₀ alcohol substituted with halogen, C₂-C₂₀ ether substituted with halogen, C₂-C₂₀ carboxylic acid substituted with halogen, C₃-C₂₀ ester substituted with halogen, C₃-C₂₀ β-diketone substituted with halogen, C₁-C₂₀ amine substituted with halogen, C₆-C₂₀ arene substituted with halogen, C₄-C₂₀ cyclic alkane substituted with halogen and C₃-C₂₀ cyclic ether substituted with halogen.

[0021] The neutral ligand L is selected from the group consisting of CO, CS, CS₂, RCN, RNC, OR₂, SR₂, NR₃, PR₃, NR₂R′, PR₂P′, ROR′, RSR′, C₂-C₂₀ alkylidene, C₂-C₂₀ alkylidyne, C₄-C₂₀ cyclic alkylidene, C₄-C₂₀ diene, C₆-C₂₀ triene, C₄-C₂₀ cyclic diene, C₂-C₂₀ cyclic triene, C₆-C₂₀ arene, C₂-C₂₀ ether, C₁-C₂₀ amine, C₃-C₂₀ cyclic ether, RCN substituted with halogen, RNC substituted with halogen, OR₂ substituted with halogen, SR₂ substituted with halogen, NR₃ substituted with halogen, PR₃ substituted with halogen, NR₂R′ substituted with halogen, PR₂P′ substituted with halogen, ROR′ substituted with halogen, RSR′ substituted with halogen, C₂-C₂₀ alkylidene substituted with halogen, C₂-C₂₀ alkylidyne substituted with halogen, C₄-C₂₀ cyclic alkylidene substituted with halogen, C₄-C₂₀ diene substituted with halogen, C₆-C₂₀ triene substituted with halogen, C₄-C₂₀ cyclic diene substituted with halogen, C₂-C₂₀ cyclic triene substituted with halogen, C₆-C₂₀ arene substituted with halogen, C₂-C₂₀ ether substituted with halogen, C₁-C₂₀ amine substituted with halogen and C₃-C₂₀ cyclic ether substituted with halogen. Here, R and R′ are individually selected from the group consisting of H, C₁-C₁₀ alkyl and C₁-C₁₀ alkyl substituted with halogen.

[0022] The anion ligand X is selected from the group consisting of H, F, Cl, Br, I, C₁-C₁₀ alkyl, C₂-C₁₀ alkenyl, C₁-C₈ alkoxy, C₆-C₁₂ aryl, β-diketonate, cyclopentadienyl, C₁-C₈ alkylcylcopentadienyl, C₁-C₁₀ alkyl substituted with halogen, C₂-C₁₀ alkenyl substituted with halogen, C₁-C₈ alkoxy substituted with halogen, C₆-C₁₂ aryl substituted with halogen, β-diketonate substituted with halogen, cyclopentadienyl substituted with halogen and C₁-C₈ alkylcylcopentadienyl substituted with halogen.

[0023] The metal precursor M(L)X further comprises the neutral ligand L in an amount ranging from 0.1 to 50 wt %. Also, the metal precursor further comprises HX in an amount ranging from 0.1 to 50 wt %. Here, X is the above-described anion ligand.

[0024] The step (b) is performed at the presence of a catalyst selected from the group consisting of HF, HCl, HBr, HI, F₂, C₁₂, Br₂, I₂, C₁-C₁₀ alkane substituted with halogen, C₂-C₁₀ alkane substituted with halogen, C₁-C₈ alkoxide substituted with halogen, C₆-C₁₂ arene substituted with halogen, β-diketonate substituted with halogen, cyclopentadiene substituted with halogen and C₁-C₈ alkylcyclopentadiene.

[0025] The metal precursor M(L)X may be easily deposited as metal film according to the following disproportionate reaction. In addition, the M(L)X may be deposited at relatively low temperature because electrons are exchanged between the same metals.

Metal reaction formula: 3M⁺→2M+M³⁺

Overall reaction formula: 3M(L)X→2M+MX₃+3L

BRIEF DESCRIPTION OF THE DRAWINGS

[0026]FIGS. 1 and 2 are cross-sectional diagrams illustrating the reaction mechanisms of the metal film deposition according to this disclosure.

DETAILED DESCRIPTION OF THE PRESENTLY PREFERRED EMBODIMENTS

[0027] The CVD method performed according to the above-described reaction principle will be explained referring to FIGS. 1 and 2.

[0028] Referring to FIG. 1, metal precursor 2 such as pure solid state of M(L)X or a M(L)X solution having a molarity ranging from 0.05 M to 10M is sent from a source supply to a vaporizer using carrier gas such as argon or nitrogen. The metal precursor 2 is vaporized in the vaporizer and then provided to a reactor to be adsorbed on a surface of a semiconductor substrate 1 pre-heated to a temperature ranging from 100 to 900° C.

[0029] Referring to FIG. 2, the adsorbed metal precursor 2 absorbs heat from the surface of the substrate 1 pre-heated to a temperature ranging from 100 to 900° C., and then decomposes according to the above-described reaction formulas. As a result, metal films 3 are formed. Here, M is a metal, preferably cobalt, rhodium or iridium, L is neutral ligand and X is anion ligand. The side-products (MX₃) 4 and neutral ligand (L) 5 generated from the process are easily pumped out using vacuum due to their high vapor pressure.

[0030] When the M(L)X solution is used as the metal precursor, solvent is preferably C₁-C₂₀ alkane, C₂-C₂₀ alkene, C₂-C₂₀ alkyne, C₁-C₂₀ alcohol, C₂-C₂₀ ether, C₂-C₂₀ carboxylic acid, C₃-C₂₀ ester, C₃-C₂₀ β-diketone, C₁-C₂₀ amine, C₆-C₂₀ arene, C₄-C₂₀ cyclic alkane, C₃-C₂₀ cyclic ether, C₁-C₂₀ alkane substituted with halogen, C₂-C₂₀ alkene substituted with halogen, C₂-C₂₀ alkyne substituted with halogen, C₁-C₂₀ alcohol substituted with halogen, C₂-C₂₀ ether substituted with halogen, C₂-C₂₀ carboxylic acid substituted with halogen, C₃-C₂₀ ester substituted with halogen, C₃-C₂₀ β-diketone substituted with halogen, C₁-C₂₀ amine substituted with halogen, C₆-C₂₀ arene substituted with halogen, C₄-C₂₀ cyclic alkane substituted with halogen or C₃-C₂₀ cyclic ether substituted with halogen.

[0031] The neutral ligand L5 is preferably CO, CS, CS₂, RCN, RNC, OR₂, SR₂, NR₃, PR₃, NR₂R′, PR₂P′, ROR′, RSR′, C₂-C₂₀ alkylidene, C₂-C₂₀ alkylidyne, C₄-C₂₀ cyclic alkylidene, C₄-C₂₀ diene, C₆-C₂₀ triene, C₄-C₂₀ cyclic diene, C₂-C₂₀ cyclic triene, C₆-C₂₀ arene, C₂-C₂₀ ether, C₁-C₂₀ amine, C₃-C₂₀ cyclic ether, RCN substituted with halogen, RNC substituted with halogen, OR₂ substituted with halogen, SR₂ substituted with halogen, NR₃ substituted with halogen, PR₃ substituted with halogen, NR₂R′ substituted with halogen, PR₂P′ substituted with halogen, ROR′ substituted with halogen, RSR′ substituted with halogen, C₂-C₂₀ alkylidene substituted with halogen, C₂-C₂₀ alkylidyne substituted with halogen, C₄-C₂₀ cyclic alkylidene substituted with halogen, C₄-C₂₀ diene substituted with halogen, C₆-C₂₀ triene substituted with halogen, C₄-C₂₀ cyclic diene substituted with halogen, C₂-C₂₀ cyclic triene substituted with halogen, C₆-C₂₀ arene substituted with halogen, C₂-C₂₀ ether substituted with halogen, C₁-C₂₀ amine substituted with halogen or C₃-C₂₀ cyclic ether substituted with halogen. Here, R and R′ are preferably H, C₁-C₁₀ alkyl or C₁-C₁₀ alkyl substituted with halogen.

[0032] The anion ligand X is preferably H, F, Cl, Br, I, C₁-C₁₀ alkyl, C₂-C₁₀ alkenyl, C₁-C₈ alkoxy, C₆-C₁₂ aryl, β-diketonate, cyclopentadienyl, C₁-C₈ alkylcylcopentadienyl, C₁-C₁₀ alkyl substituted with halogen, C₂-C₁₀ alkenyl substituted with halogen, C₁-C₈ alkoxy substituted with halogen, C₆-C₁₂ aryl substituted with halogen, β-diketonate substituted with halogen, cyclopentadienyl substituted with halogen or C₁-C₈ alkylcylcopentadienyl substituted with halogen.

[0033] In order to stabilize the metal precursor M(L)X during the deposition process of the metal films 3, additional neutral ligand (L) 5 in an amount ranging from 0.1 to 50 wt % may be added in the metal precursor. HX (X=anion ligand) in an amount ranging from 0.1 to 50 wt % may be added in the metal precursor to achieve the same objective.

[0034] Additionally, when materials including halogen are added, reaction speed is increased due to catalyst reaction.

[0035] Here, a catalyst is preferably HF, HCl, HBr, HI, F₂, Cl₂, Br₂, I₂, C₁-C₁₀ alkane substituted with halogen, C₂-C₁₀ alkane substituted with halogen, C₁-C₈ alkoxide substituted with halogen, C₆-C₁₂ arene substituted with halogen, β-diketonate substituted with halogen, cyclopentadiene substituted with halogen or C₁-C₈ alkylcyclopentadiene.

[0036] As discussed earlier, metal films having high purity may be deposited without impurities such as carbon, hydrogen or oxygen by using disproportionate reaction at low temperature because side-products such as L and MX₃, which are neutral materials having high vapor pressure, are easily removed from a reactor by vacuum without remaining in the films. Additionally, almost no particles are generated because a reaction gas is not used. 

What is claimed is:
 1. A method for manufacturing a metal film comprising: (a) vaporizing a metal precursor M(L)X, where M is a metal, L is a neutral ligand and X is an anion ligand, wherein the metal M has an oxidation number of +1; (b) adsorbing the vaporized metal precursor on a semiconductor substrate heated to a temperature ranging from 100 to 900° C. to deposit metal layer on the substrate; and (c) pumping out the side-product generated during the step (b).
 2. The method according to claim 1, wherein the metal M is selected from the group consisting of cobalt, rhodium and iridium.
 3. The method according to claim 1, wherein the metal precursor is pure solid state of M(L)X or a M(L)X solution having a molarity ranging from 0.05 to 10M.
 4. The method according to claim 3, wherein solvent used in the M(L)X solution is selected from the group consisting of C₁-C₂₀ alkane, C₂-C₂₀ alkene, C₂-C₂₀ alkyne, C₁-C₂₀ alcohol, C₂-C₂₀ ether, C₂-C₂₀ carboxylic acid, C₃-C₂₀ ester, C₃-C₂₀ β-diketone, C₁-C₂₀ amine, C₆-C₂₀ arene, C₄-C₂₀ cyclic alkane, C₃-C₂₀ cyclic ether, C₁-C₂₀ alkane substituted with halogen, C₂-C₂₀ alkene substituted with halogen, C₂-C₂₀ alkyne substituted with halogen, C₁-C₂₀ alcohol substituted with halogen, C₂-C₂₀ ether substituted with halogen, C₂-C₂₀ carboxylic acid substituted with halogen, C₃-C₂₀ ester substituted with halogen, C₃-C₂₀ β-diketone substituted with halogen, C₁-C₂₀ amine substituted with halogen, C₆-C₂₀ arene substituted with halogen, C₄-C₂₀ cyclic alkane substituted with halogen and C₃-C₂₀ cyclic ether substituted with halogen.
 5. The method according to claim 1, wherein the neutral ligand L is selected from the group consisting of CO, CS, CS₂, RCN, RNC, OR₂, SR₂, NR₃, PR₃, NR₂R′, PR₂P′, ROR′, RSR′, C₂-C₂₀ alkylidene, C₂-C₂₀ alkylidyne, C₄-C₂₀ cyclic alkylidene, C₄-C₂₀ diene, C₆-C₂₀ triene, C₄-C₂₀ cyclic diene, C₂-C₂₀ cyclic triene, C₆-C₂₀ arene, C₂-C₂₀ ether, C₁-C₂₀ amine, C₃-C₂₀ cyclic ether, RCN substituted with halogen, RNC substituted with halogen, OR₂ substituted with halogen, SR₂ substituted with halogen, NR₃ substituted with halogen, PR₃ substituted with halogen, NR₂R′ substituted with halogen, PR₂P′ substituted with halogen, ROR′ substituted with halogen, RSR′ substituted with halogen, C₂-C₂₀ alkylidene substituted with halogen, C₂-C₂₀ alkylidyne substituted with halogen, C₄-C₂₀ cyclic alkylidene substituted with halogen, C₄-C₂₀ diene substituted with halogen, C₆-C₂₀ triene substituted with halogen, C₄-C₂₀ cyclic diene substituted with halogen, C₂-C₂₀ cyclic triene substituted with halogen, C₆-C₂₀ arene substituted with halogen, C₂-C₂₀ ether substituted with halogen, C₁-C₂₀ amine substituted with halogen and C₃-C₂₀ cyclic ether substituted with halogen, where R and R′ are individually selected from the group consisting of H, C₁-C₁₀ alkyl and C₁-C₁₀ alkyl substituted with halogen.
 6. The method according to claim 1, wherein the anion ligand X is selected from the group consisting of H, F, Cl, Br, I, C₁-C₁₀ alkyl, C₂-C₁₀ alkenyl, C₁-C₈ alkoxy, C₆-C₁₂ aryl, β-diketonate, cyclopentadienyl, C₁-C₈ alkylcylcopentadienyl, C₁-C₁₀ alkyl substituted with halogen, C₂-C₁₀ alkenyl substituted with halogen, C₁-C₈ alkoxy substituted with halogen, C₆-C₁₂ aryl substituted with halogen, β-diketonate substituted with halogen, cyclopentadienyl substituted with halogen and C₁-C₈ alkylcylcopentadienyl substituted with halogen.
 7. The method according to claim 1, wherein the metal precursor further comprises a neutral ligand in an amount ranging from 0.1 to 50 wt %.
 8. The method according to claim 1, wherein the metal precursor further comprises HX in an amount ranging from 0.1 to 50 wt % wherein X is an anion ligand.
 9. The method according to claim 1, wherein step (b) is performed at the presence of a catalyst selected from the group consisting of HF, HCl, HBr, HI, F₂, Cl₂, Br₂, I₂, C₁-C₁₀ alkane substituted with halogen, C₂-C₁₀ alkane substituted with halogen, C₁-C₈ alkoxide substituted with halogen, C₆-C₁₂ arene substituted with halogen, β-diketonate substituted with halogen, cyclopentadiene substituted with halogen and C₁-C₈ alkylcyclopentadiene.
 10. The method according to claim 1, wherein parts (a) to (c) are performed using a CVD(chemical vapor deposition) method.
 11. A CVD method using a precursor M(L)X as a source, where M is a metal, L is a neutral ligand and X is an anion ligand, wherein the metal has an oxidation number of +1.
 12. The CVD method according to claim 11, the method being performed in the absence of oxygen or hydrogen as a reaction gas. 